"I purchased the Siemens RWB27, since I have a combi, and did not require separate hot water and central heating controls. The documentation provided with the RWB27 is concise and easy to understand. Once the wiring was done, it was very straight forward to set up all the time programs. The switches on the reverse on the unit allow configuration of the timings and whether two or three periods are required. It is permanently lit up and so it is easy to view All in all – a very nice and easy timer to use."
"I bought this timer because it fitted the existing backplate and I didn't have to rewire anything in my case. The factory preset time wasn't correct, around 20 minutes out, but this was soon sorted. The controls are simple to use, the programming is easy once you have the hang of what is going on, and it's possible to do this after only a brief look at the instructions which is a sign of how well it's organised. I set my timer for 5 days plus 2 days so that I could have different times for the weekend, other options are available and can be set on the DIP switches at the back. I've not used the other modes and can't comment on how the differ or work. The 'over-ride' works well and logically and a nice feature is the '1Hr' boost; press it twice and you get two hours, neat. The unit looks good on the wall, and has a permanently-on backlight, I hope this lasts because it will be difficult to see if it doesn't. Altogether a decent and modern timer at a reasonable price."
"One thing I would have expected this type of unit to have would be a simple override switch. i.e. to be able to just turn on/off in whatever mode was current. This function is possible but not without a lot of button pushing and then the same in reverse when you want to restore the program function. If I'd have known about this before I'd fitted it, I would have chosen a different unit."